Technical Abstract:
Ammonia volatilization from surface applied urea-based sources of nitrogen (N) may reduce the efficiency of N fertilizers and the availability of N to crops. Nitrogen losses through ammonia volatilization are greater during summer months because N fertilizers are applied in conditions of high temperatures and rapid soil drying. It has been reported that N losses through ammonia volatilization can be 50 % of total N applied depending on the source of N used and soil and environmental factors. Nitrogen stabilizers may reduce volatilization losses enabling the use of less expensive urea fertilizers. During the unusually hot and dry summer of 2007, we compared two N stabilizers (Agrotain® and calcium chloride) on ammonia volatilization from urea and UAN fertilizers (applied at a rate of 134 kg N ha-1). Atmospheric ammonia was measured at 0, 1, 2, 3, 5, 8 and 17 days after fertilizer application, in two different field conditions, 1) soil covered with rye (Secale cereale L.) residue and (2) bare soil. Treatments for each situation were: 1) Control (no N added), 2) urea, 3) urea+Agrotain®, 4) UAN, 5) UAN+Agrotain ® and 6) UAN+ CaCl2. In both field conditions, the use of Agrotain ® mixed with urea significantly (P ‰¤0.05) reduced the rate of ammonia volatilization, accumulated ammonia losses and the fraction of N volatilized from the fertilizer, when compared to urea alone. UAN+Agrotain ® and UAN+CaCl2 treatments did not reduce accumulated ammonia losses and the fraction of N volatilized from the fertilizer, when compared to UAN alone.